1. Field of the Invention
This invention relates to a method of and apparatus for applying a saturant to a moving sheet material and, more particularly, to the method of and apparatus for metering a fast-reacting saturant onto moving sheet material.
2. Description of the Prior Art
U.S. Pat. No. 428,188 teaches a device for the rubber-striping of waterproof fabrics. This device uses a trough having a series of openings through its bottom spaced along the length of the trough. A shallow channel or channels lead transversely from each of these openings. The trough serves as a reservoir for the rubber-striping compound, which passes through the openings and transverse channels leading from these openings to form stripes on the fabric as the fabric moves in surface contact with the bottom of the trough. Although the apparatus of the invention described herein may be considered somewhat similar to the rubber-striping device, there are several important differences. One such difference is that there is only one continuous slot through the bottom of the trough in the invention as opposed to a series of openings in the patented device. Another difference is the absence of transverse channels leading from either longitudinal edge of the slot of the invention. Still another difference is that the metering achieved by the invention described herein is from the co-action of a threaded rod placed over the slot so that it contacts the upper longitudinal edges of the slot through the bottom of the trough. The method of the invention described herein also differs from the teaching of U.S. Pat. No. 428,188 in that it is essential to have no larger reservoir in the trough than can be metered through the slot in the trough and onto the sheet material in less time than it takes for the fast-reacting saturant to set-up or cure. The rubber-striping device teaches the use of a large reservoir of rubber-coating compound in the trough with no concern for applying the rubber compound to the moving fabric before the rubber compound cures.
U.S. Pat. No. 3,110,919 teaches a coater for spreading photo-sensitive material over conventional screen material. The method and apparatus of the invention described herein is concerned with metering a fast-reacting saturant onto moving sheet material. The patent teaches a flexible bar with a series of grooves around its circumference as an alternative to the helically wound spring which is defined as that part of the apparatus which applies the coating of photo-sensitive material to the screen, it being noted that it is the flexibility of the bar which will lead to the application of a substantially uniform coating. The method and apparatus of the invention described herein uses a threaded rod co-acting with the upper longitudinal edges of the slot in the bottom of the trough as a metering device, it being of no particular consequence whether the threaded rod be flexible or rigid. Also, the threaded rod of the invention herein does not contact the moving sheet material being coated as does the flexible bar of the patent when applying a coating to a screen.
U.S. Pat. No. 3,045,273 teaches the use of a threaded elongated member supported from above and positioned against one edge of a lower chamber wall in association with compressed air in the chamber to clean a surface of material moving thereunder, the threads forming a plurality of high velocity ports which produce considerable turbulence of the air emanating therefrom. A vacuum system adjacent the turbulent air producing apparatus assists in cleaning the surface of the material moving thereunder. There are several important differences between the method and apparatus of the invention described herein and the teaching of U.S. Pat. No. 3,045,273. One such difference is that the invention is directed to metering a fast reacting saturant onto moving sheet material and not concerned with cleaning a surface of moving material. Other differences are that the threaded rod of the invention is removably (not fixedly) supported from below (not above) and is in contact with two (not one) edges of a slot. Still another difference is that the invention does not use a vacuum whereas a vacuum is an integral part of the teaching of U.S. Pat. No. 3,045,273.